Rolls of light sensitive paper and film require light-tight packaging so that such rolls are not exposed to white or room light whereby the light sensitive characteristics of the rolls would be damaged. While such packaging must be light-tight, such packaging needs to facilitate the loading of the rolls in room light into cooperating apparatus which dispense or otherwise use the paper or film.
U.S. Pat. No. 4,148,395, commonly assigned, discloses a package which includes a pair of flexible opaque end disks or covers attached to the ends of a core of the roll, and an opaque leader attached to a leading end of the length of paper or film forming the roll. A peripheral portion on each end disk is folded over and adhered to an edge of an underlying convolution of the leader. A layer of adhesive is provided on the underside of the peripheral portion prior to folding over. When the leader is pulled away from the packaged roll, the end disks tear circumferentially at the edge of the roll; so that, the peripheral portion remains adhered to the leader. However, since the folded over portions tend to crimp or fold unevenly, passages for light tend to be formed between the folded over portions and the leader, which can allow light to reach and damage the paper or film.
U.S. Pat. No. 5,133,171, commonly assigned, discloses a package which includes a pair of similar end disks and a leader. After a first convolution of the leader is wrapped on the roll, peripheral portions of the end disks are folded over the first convolution. A second convolution is then wrapped onto the roll to capture the folded-over peripheral portions between the first and second convolutions and to make the package light tight. Friction is relied upon to retain the folded-over portions between the convolutions of leader and no adhesive is used. However, the frictional engagement between the folded-over portions and the convolutions of the leader occasionally is not sufficient to prevent the folded-over portions from slipping at least partially free, thereby permitting entry of light and damage to the product. The requirement for a second full convolution also adds expense to the product and produces additional waste material for the customer.
Research Disclosure No. 22932 of May 1993 shows a package in which the end disks have the same diameter as the roll. A strip of adhesive tape is wrapped around each of the circumferential edges of an outer convolution of the leader and then folded over onto the end disk. The folded over portions of the tape strips tend to crimp or fold unevenly, so that passages for light tend to be formed between the folded over portions and the end disks, which can allow light to reach and damage the paper or film. Extra components, such as an enclosing bag, may be necessary to ensure light tightness.
U.S. Pat. No. 5,353,933 discloses a package in which a light-shielding leader with covers is connected to the end of a photosensitive strip of material. The leader is wound twice around the roll, and the side edges of the covers are inserted into the core and fixed by the insertion of a bushing into the core with pressure. A notch is formed in the covers to ensure and facilitate opening at the forward end of the covers. When the leader is drawn, a pulling force acts on the notch, and the covers are torn along adhesion outside boundaries. Once torn, the covers extend or fan outwards from the core, which may adversely affect the ease of rotation when unwinding the web material from the core, resulting in image disturbance if an image is applied during unwinding. In addition, the extended covers may fold over if the web is re-wound back onto the roll, causing scratching of the photosensitive material. Further, providing notches in the covers results in an extra manufacturing step, and may tend to form light passages.